Once the first sign of madness, talking out loud with no other person visible alongside us is now universally recognised as the norm - providing, of course, that a hand-held device is in evidence.
But reception is often weak on cell phones and in ear pieces, and when people can't hear well they assume that the person they are talking to is having the same difficulty and so increase their volume accordingly.
Cocooned as far as their own brains are concerned by what is happening in their own ears, such talkers focus in on their specific information exchange, while instinctively speaking as though they were in a noisy space.
Unfortunately, all too often, the space they are in is filled with many unconnected people who simply want to work on their own business plans, concentrate on their own materials, carry on other low key conversations or attend to their own thoughts.
Because loudmouthed invaders of privacy have become ubiquitous, those afflicted by them have learned to iSolate themselves with iPhones, block ears with Nokias, bury themselves in Blackberries or utilise any other implement that will blot out the unwanted information.
But surprisingly rarely does anyone to ask an offender to speak more quietly.
Despite ourselves, if we can't block our ears the information in any conversation will impel our curiosity.
The intrusive voice may cause irritation, embarrassment, amusement, anger or genuine interest - but no one can ignore it completely. Why? Because those on mobile phones are rarely shouting but rather projecting their voices with natural ease.
Strongly spoken, easeful words have the power to inject ideas into other people whether they listen willingly or not. Were those people asked to recall what was behind the speaker they were overhearing, however, most would find it hard to do so.
Those of us who have to present ideas to others and chose to rely heavily on Powerpoint, Keynote, Prezi or any other slide format packed with scarcely visible words to deliver the necessary information should take a lesson from the evidence that cell phone use in crowded spaces reveals.
Tongue and voice working well together impel ears to receive and brains to connect with what is being pointed out more effectively than any printed words can do. And any one determined not to pay attention will simply insert earphones and tune into a pitch of their own choosing.
When you practise to deliver a convincing message, speak as if you are on a mobile phone in a noisy area. You will discover that by intending to be heard you automatically achieve the vocal pitches and volume necessary to connect you to your anticipated, real audience.
Voice and presence are the most powerful tools at a presenter's disposal. They cost nothing, They are feather light to carry. They can never be left behind. Most important of all they will always give warning well in advance of arriving at a venue that they are likely to malfunction.